Non-Systematic Complex Number RS Coded OFDM by Unique Word Prefix

Huemer, Mario; Hofbauer, Christian; Huber, Johannes B.

doi:10.1109/tsp.2011.2168522

Cited by 62 publications

(76 citation statements)

References 24 publications

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“…In UW-OFDM, this guard interval is part of the DFT interval, i.e., the last N u samples of the DFT interval are reserved for the unique word, which is a sequence of known samples. In [1], it is shown that UW-OFDM outperforms cyclic prefix (CP-) OFDM with respect to the bit error rate in fading channels. This is confirmed in [2] where a theoretical analysis of the error rate performance shows that UW-OFDM is always able to achieve full diversity, whereas in CP-OFDM only a diversity one is obtained unless precoding is used.…”

Section: Uw-ofdmmentioning

confidence: 99%

Design and analysis of the UW-OFDM signal

Steendam

2014

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP)

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Unique word (UW-) OFDM is a novel multicarrier system that is shown to be suitable for cognitive radio systems. To construct the UW-OFDM signal, a code generation matrix is required to introduce redundancy in the frequency domain, implying that the code generation matrix must satisfy a number of conditions. In this paper, we use an algebraic construction method to separate the conditions imposed by the signal shape from the code design. The degrees of freedom resulting from this construction method are used to optimize different performance measures (i.e., the minimum Euclidean distance and the power) at the transmitter or at the receiver side. Based on the algebraic decomposition, a composite channel can be defined. Irrespective of whether the optimization is done at the transmitter or the receiver, we shown in the paper that always the strongest modes of this composite channel must be excited.Index Terms-multicarrier communication, error rate, Euclidean distance, tight frame UW-OFDMIn multicarrier communication systems, typically a guard interval is used to combat the effect of intersymbol interference. In traditional multicarrier systems, this guard interval is added on top of the signal containing the data, resulting in a signal with extended symbol duration. Unlike these standard multicarrier systems, unique word (UW-) OFDM counteracts intersymbol interference without the necessity to extend the DFT block with a guard interval. In UW-OFDM, this guard interval is part of the DFT interval, i.e., the last N u samples of the DFT interval are reserved for the unique word, which is a sequence of known samples. In [1], it is shown that UW-OFDM outperforms cyclic prefix (CP-) OFDM with respect to the bit error rate in fading channels. This is confirmed in [2] where a theoretical analysis of the error rate performance shows that UW-OFDM is always able to achieve full diversity, whereas in CP-OFDM only a diversity one is obtained unless precoding is used. Further, it is shown in [3] that UW-OFDM hasThe author gratefully acknowledges the financial support from the Flemish Fund for Scientific Research (FWO). This research has been funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office. much lower out-of-band radiation compared to CP-OFDM. Hence, UW-OFDM is an excellent candidate for cognitive radio systems.To construct the UW-OFDM signal, we use the two-step approach. First, we generate the time-domain sequence corresponding to the data symbols, resulting in a block of N u zeroes at the end of the DFT interval. In this block of zeroes, we add the unique word symbols during the second step. The construction of the data contribution containing a block of zeroes in the time domain requires the presence of redundancy in the frequency domain. Consequently, assuming the DFT size equals N , a maximum of N − N u data symbols can be transmitted per DFT block.The UW-OFDM signal is generated as follows. First, the N d ≤ N − N u data symbols a d are fed to the N m × N d code...

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Section: Uw-ofdmmentioning

confidence: 99%

Design and analysis of the UW-OFDM signal

Steendam

2014

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP)

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“…The redundant carrier symbols and the energy assigned to them depend on the choice of P through M. By using (4) in (1), it can be seen that the redundant carriers introduce correlations in the frequency domain data vector x. Different redundant carrier placement approaches are introduced such that the energy spent on redundant carriers is minimized [15], [16].…”

Section: −1mentioning

confidence: 99%

“…In a two-step implementation of UW-OFDM systems, first a block of zeros is constructed at the tail of the IDFT output. This can be done by two approaches [4]: 1) by appropriately loading a set of redundant carriers in systematic coded UW-OFDM system, i.e. data carriers and redundant carriers are separated, and 2) by distributing the redundancy over all active subcarriers by using a code generator matrix in non systematic coded UW-OFDM system.…”

Section: Introductionmentioning

confidence: 99%

“…Contrary to the CP which is random, the unique word is deterministic and can be designed for some practical needs such as synchronization or channel estimation. Although the UW-OFDM frame is shorter than CP-OFDM and contains lower number of data symbols, the bit error rate and throughput of UW-OFDM is comparable to those of CP-OFDM [3], [4].…”

Section: Introductionmentioning

confidence: 99%

“…To our best knowledge, the spectrum for UW-OFDM is only considered in [4], where the authors claim that UW-OFDM has lower out-of-band radiation than CP-OFDM. These results were based on simulations only.…”

Section: Introductionmentioning

confidence: 99%

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Power Spectrum Characterization of Systematic Coded UW-OFDM Systems

Rajabzadeh

Steendam

Khoshbin

2013

2013 IEEE 78th Vehicular Technology Conference (VTC Fall)

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Abstract-Unique word (UW)-OFDM is a newly proposed multicarrier technique that has shown to outperform cyclic prefix (CP)-OFDM in fading channels. Until now, the spectrum of UW-OFDM is not thoroughly investigated. In this paper, we derive an analytical expression for the spectrum taking into account the DFT based implementation of the system. Simulations show that the proposed analytical results are very accurate. Compared to CP-OFDM, we show that UW-OFDM has much lower out-ofband (OOB) radiation, which makes it suitable for systems with strict spectral masks, as e.g. cognitive radios. Further, in this paper, we evaluate the effect of the redundant carrier placement on the spectrum.

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On the Diversity Order of UW-OFDM

Steendam¹

2014

IFIP Advances in Information and Communication Technology

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International audienceUnique word (UW) OFDM is a multicarrier technique that follows a different approach than standard multicarrier techniques like cyclic prefix (CP) OFDM. It has been reported that UW-OFDM outperforms CP-OFDM in the sense that it performs better in fading channels [1, 2], and it has much lower out-of-band radiation [3] compared to CP-OFDM. However, a theoretical analysis of the error rate performance of UW-OFDM was never addressed in the literature. In this paper, we derive analytical expressions for the bit error rate for UW-OFDM, from which we can obtain the diversity order. It turns out that when the code generator matrix, needed to construct the UW-OFDM signal, is full rank, the UW-OFDM system reaches the maximum diversity order. This is in contrast with standard CP-OFDM, where only diversity order one can be reached, unless additional precoding is applied. Further, in the paper, we propose a construction method for the code generator matrix to achieve a (close to) maximum coding gain

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Non-Systematic Complex Number RS Coded OFDM by Unique Word Prefix

Cited by 62 publications

References 24 publications

Design and analysis of the UW-OFDM signal

Design and analysis of the UW-OFDM signal

Power Spectrum Characterization of Systematic Coded UW-OFDM Systems

On the Diversity Order of UW-OFDM

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